Where in your keezer do you put your temperature controller probe?

My Chest freezer has a little 'step' where I've been sitting my temperature probe in a jar of water. After having problems with astringency in my beers recently, it finally hit me -- cold air sinks. I took a temp reading at my step (37 degrees) and then at the base of my chest freezer -- 26 degrees!!!

Beers I have been trying to hit at 2.5 volumes could be well over 3 volumes at that temperature.

So where do you put your keezer probe?

I leave it in the bottom, or taped to the fermenter If I have something 'working'.

You might consider rigging up a small DC fan to keep your temperature consistent in there.

Rick500 said:

You might consider rigging up a small DC fan to keep your temperature consistent in there.

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I was thinking the same thing-- I wonder if the moisture would present a problem...

Yeah, you're right, probably a bucket o' Damp Rid too.

Rick500 said:

Yeah, you're right, probably a bucket o' Damp Rid too.

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There's no way I'm the only homebrewer to figure this out...maybe putting it on the bottom is the solution. My question is what temperature is the actual beer...

I just listened to the July 13th Brew Strong podcast earlier today, and Jamil was saying if you don't want to use a Fermcap, the most accurate temperature measurement is going to be by taping the probe to the fermenter, at about the midpoint (vertically) of the column of beer. The podcast is well worth a listen.

I've never understood what's wrong with just pouring a nice tall glass and shoving the probe right in the beer. My keezer reads 47 but the temp of the actual beer is always around 3 degrees cooler.

Rick500 said:

I just listened to the July 13th Brew Strong podcast earlier today, and Jamil was saying if you don't want to use a Fermcap, the most accurate temperature measurement is going to be by taping the probe to the fermenter, at about the midpoint (vertically) of the column of beer. The podcast is well worth a listen.

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I may do this. I know that works for the glass of a carboy -- does it work for the stainless steel of a corny too?

my temp probe is in a 20oz bottle of water. I made a hole in the cap to feed the probe in, then hot glued it closed so i can't spill it.

the bottle sits on the floor of the keezer on the back wall next to 2 kegs. I keep it set at 40deg and my air temp thermometer is always between 36 and 42

I came to the same problem this weekend when building/testing my keezer. My solution: I wired three small computer fans to a DC adapter. I screwed them all onto a board of wood about 3 feet tall, about 6-8 inches apart. Then i just place the board vertical into the keezer. That way I'm getting movement low, mid, and high in the keezer. Also putting in some moisture control to keep things dry in there.

Finally, (and this final phase is still in the experimentation phase) I'm going to put my temperature probe into a stainless steel toilet/sink supply tube. Crimp the bottom. Put some solder in there and heat/melt from the outside to try to create a little more of a water barrier. Then put that SS tube (with the probe in it) into a SMALL vial of StarSan through a cut-out screwtop--maybe a white labs vial. I don't want too much water surrounding the thermowell b/c I fear it may retain the temperature TOO well. That vial w/ the SS tube w/ the probe will be mounted on the other side of my "fan board" setup, just a little ways off the floor of the keezer, and a little bit away from the walls where the cooling coils are.

Rick500 said:

I just listened to the July 13th Brew Strong podcast earlier today, and Jamil was saying if you don't want to use a Fermcap, the most accurate temperature measurement is going to be by taping the probe to the fermenter, at about the midpoint (vertically) of the column of beer. The podcast is well worth a listen.

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I still think he's flat-out wrong though. Yes, ideally you want to control the temp of the beer, but the keezer doesn't COOL the beer. It cools air. Liquid has a much higher thermal mass and will converge on the average temp of the surrounding air with VERY little fluctuation. By taping the probe to the fermenter, you're allowing the beer to fluctuate over the full differential range; 4 deg on the analog Johnson Controller.

One small advantage to sticking the probe to the fermenter is the keezer will last longer as it'll cycle less. I prefer more stable fermentation temps however and I've tested both ways (along with the probe in a mason jar of water), and reading air temp gave by far the most stable fermenter temps, according to the stick-ons I use.

Stevorino said:

My Chest freezer has a little 'step' where I've been sitting my temperature probe in a jar of water. After having problems with astringency in my beers recently, it finally hit me -- cold air sinks. I took a temp reading at my step (37 degrees) and then at the base of my chest freezer -- 26 degrees!!!

Beers I have been trying to hit at 2.5 volumes could be well over 3 volumes at that temperature.

So where do you put your keezer probe?

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I had this EXACT same problem about two weeks ago for my first kegging batch. My probe was on the compressor "hump" too and set at 38F. The bottom of the keezer was 26F. Because of the lower temps, my beer absorbed too much co2 and I was getting all foam at the tap.

I realized my error and moved the probe to the bottom of the keezer, and had gone through ridiculous lengths to figure out my foaming issue, including co2 pressure, line length, possible infection, and concluded it was the temp issue. I had to decarbonate my beer by purging and leaving the keg for a number of days. I've since put her back on the gas, and hope to be properly carbonated by the weekend.

A couple of important points. If you're using one of the old controllers with fixed 4F differential, then sure, measure the air. You're kind of just choosing the lesser of two evils. Really the best thing is to scrap that controller and get a digital one where you can set a 1F differential. Then you measure the temp of the beer. Tape it to the side of the fermenter (works for stainless too) and then cover it with some insulation so it is reading the beer and not influenced by the air.

It is very important to read the temp of the beer, because that is really what you're trying to control--the temp of the fermentation. If you measure anything else, it does not take into account the heat given off by fermentation and at the end of fermentation it tends to suppress yeast activity at the very time where you should be pushing it to continue. At the end you want to get the yeast to clean up all those intermediary fermentation compounds.

I hope that helps.

Oh **** -- is Pope Malty on HBT?!?!

jamilz said:

A couple of important points. If you're using one of the old controllers with fixed 4F differential, then sure, measure the air. You're kind of just choosing the lesser of two evils. Really the best thing is to scrap that controller and get a digital one where you can set a 1F differential.

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I thought about that after I posted. Your approach would indeed work better with a digital controller and tighter differential. The analog JC isn't that bad though. I've never seen more than a 1F variation on my lager ferments.

When you measure the temp of something other than the beer (vial of water, the air, etc) then when the yeast start slowing down, the result is a colder beer. This can slow the yeast activity just when you want it to keep going. Just when you want it to finish up the last of the attenuation, just when you want it to suck up that diacetyl and acetylaldehyde. That is why it is so important to measure the temp of the beer. Not for the middle of fermentation, but for the start and the end of fermentation.

Of course, it isn't the end of the world. Just chasing the perfect result.

Sounds like jamilz's method is preferable for fermenting/lagering...but for serving it seems the less perfect methods should be fine. I need to get my lager temps better dialed in because I have experienced exactly what jamilz mentioned...beer temp drops a bit towards the end of fermentation.

Serving out of my keezer...the probe in the jar on the hump reads 37 F and the beer coming out of the tap into a chilled glass reads 37 F.

Yes, serving temp is a whole other beast. If there is no fermentation to worry about, then all my comments don't apply.

I know that works for the glass of a carboy -- does it work for the stainless steel of a corny too?

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Seems like it would work better for stainless since stainless conducts heat better than glass.

Why can't you just sanitize the probe and put it in the fermenting wort itself, or would there be a risk of corrosion and off flavors from it?

cs2to4 said:

Why can't you just sanitize the probe and put it in the fermenting wort itself, or would there be a risk of corrosion and off flavors from it?

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Most probes are copper and prolonged exposure could be problematic to your yeasties.